The present invention relates to a wheel slip control system which controls the rotation of drive wheels to increase the frictional force between the drive wheels and the road surface, and more particularly to a wheel slip control system which controls the rotation of drive wheels by regulating the output power of an internal combustion engine.
Conventional wheel slip control systems control driving force to a maximum value by regulating a slip rate of drive wheels during acceleration. It is well-known that the maximum driving force is obtained when the slip rate S is approximately 10%, as shown in FIG. 2. The conventional slip control system compares drive wheel speed with follower wheel speed to determine if slip occurs during acceleration and, if slip is detected, reduces output power of an internal combustion engine.
In the abovementioned system, the difference between drive wheel speed and follower speed is used to determine the occurrence of slip. The ratio of the drive wheel speed to the follower speed should be constant when the vehicle drives at constant speed and does not slip. However, in an actual vehicle, the speed ratio usually constantly varies because of abrasion of the wheels, pneumatic pressure change or the like. Consequently, accurate slip control cannot be achieved in the prior art devices because the variable speed ratio is used as the basis for detecting slip.